This application claims the benefit of Japanese Patent Application No. 2000-119818 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a lens barrel mounted to a camera etc, and more particularly to a lens barrel constructed to prevent a deformation of an operation ring when restricting a rotation.
2. Related Background Art
A single focus lens or a zoom lens is mounted in a lens interchange type camera. The lens barrel includes a plurality of lens units each composed of a single or a plurality of optical lenses. A photographer (or an actuator incorporated into the lens barrel or a camera) properly changes a distance between the lens units, whereby focusing is performed. A main trend of the cameras over the recent years is a type of having an auto focusing mode in which the focusing is executed by the camera itself in addition to a manual focus mode in which a photographer performs the focusing by rotating a manual focus ring provided on an outer peripheral surface of the barrel. A main body of this type of camera incorporates a focusing drive mechanism constructed of a microcomputer, a CCD sensor etc. This mechanism has a structure in which when a distance to an object is detected, an electric motor built in the main body of the camera or the lens barrel moves a focusing lens unit forward or backward. On the other hand, there exists a lens barrel which, as disclosed in Japanese Patent Application Laid-Open Publication No.57-66425, includes a focusing restriction mechanism capable of focusing up to a macro photographing region within a range of only a predetermined focal length.
The lens barrel shown in FIGS. 3 and 4 is what the above focusing restriction mechanism is added to a lens barrel having the manual focus mode and the auto focus mode. A second lens unit holding frame 32 for holding a second lens unit 10 which is a focus lens unit, is slidably held within a fixed drum 1 in case of the lens barrel shown in FIGS. 3 and 4. A second pin 36 embedded into the second lens unit holding frame 32 engages with a clearance groove 42 formed in the fixed drum 1 and with a second cam groove 48 formed in a zoom cam ring 45. A drive lever 57 having a straight groove 55 extends on the side of an inner periphery of a manual focus ring 51, and the second pin 36 engages with a straight groove 55. On the other hand, a pinion 29 driven by the electric motor within the main body (unillustrated) of the camera is rotatably held at a rear side end of the fixed drum 1. This pinion 29 meshes with an internal gear ring 21 rotatably held by the fixed drum 1. A rear side end of the drive lever 57 engages with the internal gear ring 21, and the internal gear ring 21 and the drive lever 57 (i.e., the manual focus ring, 51) rotate integrally.
A rotation restricting stopper 61 movable back and forth is provided on an upper surface of the fixed drum 1. This rotation restricting stopper 61 fits in a focus ring sided engagement groove 63 when moving forward, and restricts a rotation of the manual focus ring 51 within a predetermined angular range (∞xcx9c1 m on a range marker in FIG. 4). The rotation restricting stopper 61 fits in a zoom ring sided engagement groove 65 when moving backward, and restricts a rotation of the zoom ring 53 within a predetermined angular range (50xcx9c85 mm on a focus range marker in FIG. 4). These rotational restrictions aim at meeting demands in terms of optical performance and preventing a collision between the optical systems. Note that the drive lever 57 engages with either of engagement ends 67, 69 formed on the fixed drum 1 and extending in a wide range in the direction of an optical axis, whereby the rotation of the manual focus ring 51 is, as shown in FIG. 5, restricted in the range of ∞xcx9c0.5 m on the range marker.
In the lens barrel described above, when the rotation restricting stopper 61 restricts the rotation of the manual focus ring 51, an unnecessary force might act on the manual focus ring 51 or on the drive lever 57.
The manual focus ring 51 is, when the rotation restricting stopper 61 fits in the focus ring sided engagement groove 63, restricted in its rotation within the range of ∞xcx9c1 m as described above. When auto-focusing, however, a drive control device within the main body of the camera, even after the manual focus ring 51 has rotated to a limit position of the rotational restriction, outputs a drive current to the electric motor in an extremely short period of time till it detects this and outputs a stop command. As a result, the internal gear ring 21 receives a driving force in a so-called overrun direction in spite of the manual focus ring 51 being restricted in its rotation.
On this occasion, a side end surface of the drive lever 57 engages with the engagement end 69 in the wide range on the infinity(∞)side. Therefore, the overrun of the internal gear ring 21 is hard to occur, and almost no deformation of the drive lever 57 occurs. On the 1 m side, however, if the driving force acts on the internal gear ring 21, the drive lever 57 kept in a state where one side end thereof is engaged with the rotation restricting stopper 61 through the manual focus ring 51, receives a comparatively large stress caused by a rotational moment of the internal gear ring 21 and gets flexural in an arrow direction in FIG. 6. As a consequence, the internal gear ring 21 overruns by a predetermined quantity, with the result that the drive lever 57 deforms with bending and a connecting portion between the manual focus ring 51 and the drive lever 57 is damaged. Then, for preventing these drawbacks, if a thickness of each of the manual focus ring 51 and the drive lever 57 is increased, or if a material is changed (for instance, a metal is used as a substitute for a synthetic resin used so far), it is difficult to reduce the lens barrel both in size and in weight, and, in addition, a manufacturing cost inevitably increases.
It is a primary object of the present invention, which was devised under such circumstances, to provide a lens barrel capable of preventing a deformation of an operation ring when restricting its rotation by taking a comparatively simple structure.
To accomplish the above object, according to the present invention, a lens barrel comprises an optical system provided within a main body of the barrel, an operation ring used for a photographer to operate the optical system, a driving unit, used for an electric drive, for generating a driving force transferred to the operation ring via a driving force transfer member, and a rotation restricting stopper for restricting a range of rotation of the operation ring, wherein the rotation restricting stopper is movable between a position for restricting the range of the rotation of the operation ring and a position where the range of the rotation is not restricted, and substantially simultaneously restricts a range of rotation of the driving force transfer member in the position for restricting the range of the rotation of the operation ring.
According to the present invention, the rotation restricting stopper substantially simultaneously restricts the ranges of the operation ring and of the driving force transfer member, and therefore an unnecessary force acts neither on the operation ring nor on the drive lever for connecting the operation ring to the driving force transfer member.
In lens barrel according to the present invention, it is preferable that the optical system is a focusing optical system, the operation ring is a manual focus ring, and the driving force transfer member is a ring gear. In this case, for example, the rotation restricting stopper is structured such that when its front side end fits in the focus ring sided engagement groove of the manual focus ring, its rear side end engages with an engagement protrusion formed on a ring gear to a limit of the rotational range.